Which of the following represents the correct axial distances and axial angles for the rhombohedral crystal system?

What is the total number of different types of unit cells present in the triclinic crystal system?

Which of the following crystal systems has $a = b = c$ and $\alpha = \beta = \gamma \neq 90^o$?

Select the correct option using $T$ (True) or $F$ (False) for the following statements regarding crystal systems:
$(1)$ Crystal system: Cubic,Axial distance: $a = b = c$,Axial angle: $\alpha = \beta = \gamma = 90^{\circ}$,Example: $Cu, KCl$
$(2)$ Crystal system: Monoclinic,Axial distance: $a \neq b \neq c$,Axial angle: $\alpha = \gamma = 90^{\circ}, \beta \neq 90^{\circ}$,Example: $PbCrO_4$
$(3)$ Crystal system: Trigonal (Rhombohedral),Axial distance: $a = b = c$,Axial angle: $\alpha = \beta = \gamma \neq 90^{\circ}$,Example: $CaCO_3, HgS$
$(4)$ Crystal system: Triclinic,Axial distance: $a \neq b \neq c$,Axial angle: $\alpha \neq \beta \neq \gamma \neq 90^{\circ}$,Example: $K_2Cr_2O_7, CuSO_4 \cdot 5H_2O$

For which of the following substances will $a \ne b \ne c$ and $\alpha = \beta = \gamma = 90^o$ $NOT$ hold true?

Which of the following statements is correct?